Image editing is required for many different applications such as adding 3D objects to an image such that they are consistent with the geometry depicted in the image, synthesizing realistic-looking shadows to be added to an image of a scene, creating so called “out of bounds images”, manipulating images consistently with the 3D geometry of the scenes those images depict, and many other applications. Many previous approaches have attempted to reconstruct 3D geometry of a scene from single or multiple conventional images in order to provide such image editing solutions. However, reconstructing 3D geometry in this way is complex, time consuming and computationally expensive.
Out of bounds photography is an image editing technique for converting conventional digital photographs into compelling, depth-rich images. Many examples of out of bounds images are available today, for example, on the Internet. These may comprise, for example, an image of a child running into a paddling pool in a sunny garden. A rectangular picture frame is typically manually drawn onto the image using perspective so that the frame appears to extend through the plane of the photograph. For example, the frame is drawn around the paddling pool so that the child is partly inside and partly outside the frame. Because the frame is occluded by the child the impression of depth is enhanced. Also, the background region of the image, outside the frame and excluding the child, is typically manually replaced by a plain background. In addition, shadows may be manually added to the photograph to further enhance the impression of depth.
At present, photograph editing software may be used by skilled users to manually edit digital photographs in order to produce out of bounds effects. However, this is a difficult, time consuming and complex process. Many time consuming steps are typically required to be carried out in series. This means that it is difficult to modify an out of bounds image once it has been created, without starting again from scratch. Also, when users draw a frame onto a photograph the result is often unsatisfactory because the frame does not appear to be geometrically consistent with the scene depicted in the photograph. This is sometimes the case even for skilled artists and almost always a problem for novice users.
Existing methods for generating synthetic shadows typically involve reconstructing the complete 3D scene and then using ray-tracing to generate the shadow of interest. However, it is very complex and time consuming to carry out this process especially in the case of single images.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known image processing systems for editing and/or manipulating images.